The invention lies in the field of fuel cells. The invention relates to a fuel cell system for the electrochemical generation of energy, including a fuel cell stack having membrane-electrode units, bipolar plates disposed between the units, respective end-position monopolar plates for transmitting current and guiding reaction and cooling media over the membrane-electrode units, and sealing elements. The fuel cell stack is adjoined on both sides by a current collector and an end plate, each of which have passage holes and connection ports for supplying and removing the reaction and cooling media.
In conventional fuel cells, the seal in the area where the media are supplied to and removed from the end-position monopolar plates is provided at the transitions from the connection port to the end plate, from the end plate to the current collector, and from the current collector to the adjoining media-guiding monopolar plate by respective and separate sealing elements. Therefore, the sealing costs are considerable. In addition, the two current collectors have to be sufficiently thick and, like the end plates, have to be made from a material that is chemically resistant to the reaction and cooling media.
It is accordingly an object of the invention to provide a fuel cell system for the electrochemical generation of energy that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, that provides a simple and inexpensive configuration of a sealing system for the area of the supply and removal openings for the reaction and cooling media, and that avoids the use of expensive materials for the end plates and current collectors.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a fuel cell system for the electrochemical generation of energy with reaction and cooling media, including membrane-electrode units, bipolar plates disposed between the membrane-electrode units, at least two end-position monopolar plates for transmitting current and guiding reaction and cooling media over the membrane-electrode units, the at least two end-position monopolar plates each having a side face and disposed adjacent and outside the membrane-electrode units, at least two current collectors disposed adjacent and outside the at least two end-position monopolar plates, each of the at least two current collectors having at least one collector passage hole for supplying and removing the reaction and cooling media, at least one connection port having a port end face, at least two end plates disposed adjacent and outside the at least two current collectors, each of the at least two end plates having at least one end plate passage hole communicating with the at least one connection port and the at least one collector passage hole for supplying and removing the reaction and cooling media, substantially annular sealing elements each with an opening, a respective one of the sealing elements disposed in a respective one of the at least one collector passage hole and sealingly contacting, in an area of the opening, the port end face and the side face.
The object of the invention is achieved by disposing a single, substantially annular sealing element in each passage hole in the current collector. The sealing element is in contact with the end face of the connection port and the adjoining monopolar plate in the area of the sealing element opening. The sealing element leaves clear a passage to the opening in the end-position monopolar plate and extends from the end side of the screwed-in connection port to the corresponding monopolar plate and lines the passage area from the end of the connection port to the opening in the outer media-guiding plate.
The configuration and sealing of the fuel cell system in the area where the media are supplied to and removed from the fuel cell stack provides simple, inexpensive sealing that brings with it additional advantages. Specifically, the walls of the two passage holes do not come into contact with the media for the electrochemical reaction and the cooling medium. Consequently, the end plates and current collectors do not have to be made from a chemically resistant and, therefore, expensive material. In addition, the current collector can be made from a less stable plate than before, thereby further reducing costs compared to the prior art fuel cell systems.
In accordance with another feature of the invention, each of the sealing elements is a hollow cylinder and partially projects into a respective one of the at least one end plate passage hole.
In accordance with a further feature of the invention, the at least one end plate passage hole has a given diameter substantially equal to a diameter of the at least one collector passage hole, the opening has an edge area and a diameter smaller than the given diameter, and the sealing element has an end side in the edge area bearing against the side face.
In accordance with an added feature of the invention, the at least one connection port has a thread and each of the at least two end plates has a counter-thread to the thread in the at least one end plate passage hole.
In accordance with an additional feature of the invention, the sealing elements are elastic.
In accordance with yet another feature of the invention, the at least two end-position monopolar plates have at least one end-position opening with a second given diameter and the opening of the sealing elements has a diameter substantially equal to the second given diameter.
In accordance with yet a further feature of the invention, each of the at least two current collectors is a thin-walled metal sheet.
In accordance with a concomitant feature of the invention, the at least one end plate passage hole has a given diameter substantially equal to a diameter of the at least one collector passage hole.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a fuel cell system for the electrochemical generation of energy, it is nevertheless not intended to be limited to the details shown, because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.